Process for wet spinning elastic fibers



June 11, 1968 c. E. JACKSON ET AL 3,388,200

PROCESS FOR WET SPINNING ELASTIC FIBERS Filed Dec. 21, 1964 FIG. I.

9 D N O C E S E W T E C N E w 8 E R 5'IO I5 3O 4O IMMERSION LENGTH (INCHES) FIG. 2.

u 6 0 M #1 Y $88 E OKNE N MMM 0 w u T EJ T m E A E P LDI mm LH WLP V! B United States Patent Office 3,338,200 Patented June 11, P568 ERGCESS FGR WET SPINNING ELASTKC FHEEERS Charles E. Jackson, Durham, ioyd T. Jenkins, (lary,

and Philip E. Slade, .hz, Chapel Hill, NAIL, assignors to Monsanto (Zompany, St. Louis, Mo., a corporation of Delaware Filed Dec. 21, 1964, Ser. No. 419,779 5 Claims. (Cl. 264-184) ABSTRACT OF THE DISCLOSURE The wet spinning of linear, fiber-forming, segmented polyurethane polymers is improved by positioning the spinneret so that the fiber rises vertically from the spinneret and remains in the coagulation bath for only about 0.2 seconds or less. The fiber has greater elongation than by prior wet spinning methods and retains good tenacity.

This invention relates to the preparation of shaped articles from linear, segmented polyurethane compositions and more particularly to an improved wet spinning method for the preparation of elastic fibers and filaments from linear, segmented, polyurethane polymers typified structurally by the presence of low-melting, amorphous segments joined to high-melting, crystalline segments.

Certain synthetic elastomers based on linear, segmented polyurethane polymers have been developed as a replacement for rubber, which possesses some disadvantages for textile applications that tend to offset its desirable elastic properties. Fibers from these new synthetic elastomers are highly elastic and also have a higher modulus and better abrasion resistance than rubber. It is desirable therefore, to have available a wet spinning process for the preparation of fibers and filaments from these synthetic elastomers which would have a relatively wide range of tenacities, elongations, moduli and other properties which are easily obtained in a controlled and consistently reproducible manner.

It is an object of this invention to prepare elastic fibers and filaments from linear, segmented poly-urethane polymers by an improved wet spinning process.

Another object of the invention is to provide a wet spinning process for the preparation of elastic fibers and filtments from linear, segmented polyurethane compositions in which the process is characterized by faster production rates, by the fibers remaining in the spin bath a very short period of time, approximately from about 0.025 to 0.2 second, and by the positioning of the spinneret so that the fiber leaves the spin bath at right angles to the surfaces of the spin bath and travels in an essentially vertical path upwardly to the first godet.

An additional object of the invention is to provide a wet spinning process which produces elastic polyurethan fibers of improved elongation, tenactiy, modulus and stress retention.

Yet another object of the invention is to provide a wet spinning process for the preparation of fibers from linear, segmented polyurethane compositions in which the spinneret is immersed only from about 0.5 to 3.0 inches beneath the surface of the coagulation bath and in which the elimination of substantially all friction points in the bath and on the first godet has taken place.

Other objects and advantages of the invention will become apparent from the description which follows:

Wet spinning of fiber-forming polymers wherein the polymer is extruded in a vertical upward direction with short spinneret immersion is well known in viscose spinning art. However, since viscose polymers are composed of regenerated naturally occurring cellulose rather than purely synthetic substances, the spinning conditions in viscose spinning differ radically from those in the case of wet spinning of synthetic polymers. In viscose spinning inorganic salts must be present in the coagulation bath for successful spinning of viscose dopes which contain 5-7% solids. The prior art on wet spinning of linear, segmented polyurethane polymers, as typified by US. Patents 2,755,266; 2,923,598; 2,955,07; and 2,965,437, teaches the necessity of having to use long coagulation baths and lengthy immersion time with the spinneret positioned for substantially horizontal extrusion or horizontal spinning regardless of whether the polymer is formed prior to spinning or extended in the coagulation bath.

It has unexpectedly been found that the wet spinning of linear, segmented polyurethane polymers canbe substantially improved by a process which is referred to herein as vertical spinning and may generally be described as consisting of extruding a solution of a linear, segmented polyurethane in an organic solvent into an essentially aqueous coagulation bath, withdrawing the filaments as they are coagulated upwardly through the coagulating bath a distance of from about 0.5 to 3.0 inches at a rate of Withdrawal which will result in the filaments remaining in the coagulating bath for an immersion time of from only 0.025 to 0.2 second and collecting the filaments for further processing after their emergency from the coagulating bath.

The extrusion of the linear, segmented polyurethane polymer solution may be accomplished by employing a suitable extrusion orifice well known in the art and which is suitable for the preparation of the type of end product desired. The solution of the polymer may be prepared by employing any well known prior art solvent which will dissolve a linear, segmented polyurethane polymer in the desired concentration for spinning, usually from 1525% solids concentration. Such solvents, for example, include dimethylformamide, dimethylacetamide, dimethylsulfoxide and hexamethphosphoramide. The preferred solvents are dimethylformamide and dimethylacetamide.

The coagulating bath preferably consists primarily of water at a temperature of from about 60 to C. The coagulating bath may contain a percentage of the organic solvent used to prepare the solution, for example from about 1 to 40 percent.

The positioning of the spinneret beneath the surface of the coagulting bath and the residence time of the fiber in the bath are critical features of the invention. The improvement obtainable in the wet spinning of linear, segmented polyurethane polymers is achieved by placing the spinneret in a position in the coagulating bath so that the filaments as they are extruded out of the spinneret are conveyed in an essentially vertical upward direction through the coagulating bath liquid for a distance of from about 0.5 to 3.0 inches, preferably 1.5 to 2.0 inches and at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of from about 0.025 to 0.2 second and preferably from about 0.075 to 0.1 second. Surprisingly, this very short coagulation bath exposure or residence time has been found to be advantageous in effecting coagulation and to do so without void formation. The vertical withdrawal of the filaments reduces solvent drag which is prevalent during normal wet spinning processes wherein a certain amount of the coagulating bath liquid and the spinning solvent is withdrawn partially from the surface of the coagulating bath by the moving filament and then falls back into the coagulating bath. This sets up a certain amount or drag or frictional pull on the filaments as they emerge from the coagulating bath liquid and results in deterioration of critical fiber properties. As a further means for reducing all frictional pull on the filaments during this soft stage of their development the first godet or roller around which the filaments are wrapped and removed from the coagulating bath is constructed so as to freely rotate or be driven by motor means extension of the fibers at the breaking point. Stress retention is the percent elasticity retained after 300% extension and 80% recovery of the 2nd cycle stretch.

EXAMPLE I so that no frictional pull is placed upon the filaments at this point. To a reactor vessel is added 2,000 parts by weight of Reference will now be made to the appended drawing a polycaprolactone of molecular weight 2,850, 356 parts in which: of 4,4'-methylenediphenyl diisocyanate in 1,260 parts di- FIGURE 1 is a side elevational view partly in section methylformamide solvent. The reaction is allowed to conshowing schematically an apparatus arrangement of the tinue for 1.0 to 1.5 hours. At the end of this period the type which can be used in carrying out the process of the prepolymer which results is added to a solution of 41.3 invention. parts of ethylene diamine in 12,340 parts of dimethyl- FIGURE 2 is a graph showing the effect of residence formamide to give a spinning dope of percent solids. time and immersion length on elongation, a critical prop- The spinning dope is extruded through a spinneret conerty for elastic fibers. 15 taining 15 holes of 6 mil diameter into a coagulation bath Referring now in detail to FIGURE 1, a solution of :1 containing various amounts of solvent and water at a temlinear, segmented polyurethane polymer dissolved in an perature of 70 C. Residence time, the time the filaments organic solvent is passed under pressure from a supply remain in the bath, varied from 2 to 0.75 seconds. All tank (not shown) by pump 1 through pipe 2 leading into fiber samples were washed, dried, and taken up at a the coagulating bath 3 containing an aqueous coagulating speed of 100 feet per minute. Properties of various fiber liquid 4. Then the solution is extruded through spinnerct samples using both horizontal and vertical spinneret posi- 5 in a vertical direction to form filaments 6 which are coltioning and showing the improvement in elongation oblected on advancing roller 7 and then forwarded for tained with short residence time and vertical spinning are further suitable fiber conditioning treatments. The solusummarized in Table I.

TABLE I Experi- Spinucret Time in ment No. Direction spilccBilth Bath Composition Denier Tenacity Elongation 1 2 100% water: 260 492 519 2 0. 075 .do 200 .573 55s 3 2 00% water, 10% DMF 70 .511 401 4. 0.075 215 .570 57s 5 2 75% water, D1 279 .760 516 0 0. 075 .do 232 .008 502 7 0. 075 .do 205 770 030 tion may be extruded through a single orifice or a plural- EXAMPLE II ity of orifices in the spinneret to form a filament or bundle A 3oo p,u t Onion by Wei ht of O] ,(tewrmemykne of filaments. The extruded streams of polymer are directed nlycol) of imolgcular Weight 28600 E g g with 58 5 n g D $21? ciisilifiiiil tii iiuiin ti i igtiitf iifi We =t dllsocyanate Parts tance bein from about 0.5 to 3.0 inches. The filaments 4U dlmethylformamlde solvent for P hour The lcsultmg 6 are Withdrawn by positively driven roller 7. prep-0131mm was added to a m of 0948 i of The linear, segmented polyurethane polymers which are S hyd-rat? m P g fg f fgf l i 802mm suitable for use in the improved wet spinning process of 0 glve a spmmng 0 so 1 spmmng 0pc was extruded both houzontally and vertically through a the invention include any and all of the well known linear, S imemt 15 holes of 6 mil diameter into a bqth connim segmented polyurethane polymer compositions of the s water and 25% dimeth rlformqmidg at C prior art Sometimes referred to .spandex P filas' Tl e residence time of the fiber in the spin bath was two $223 ii gi fi gg ggf ggg g seconds when spun horizontally and 0.075 second when 3,097,192 and are generally desciibed as cor npri sinmurea spun Vemcany' Thefiber fi Washed, drld and taken up segments linked to polyester or polvether segments at a .Speed of 100 feet a mmute' lfmpertms of this fi through urethane groups are given by Table II and show the improvement obtalned The process of this invention represents an impmve when using vertical short residence over horizontal long ment in the wet spun preparation of elastic fibers and filaresidence time ments from linear, segmented polyurethane polymers in EXAMPLE III several respects. Consistently reproducible elongations in A 300 part portion by Weight of a polycaprolactone excessof 500 percent are possible using the process of the consisting of 80% polycaprolactone and 20% P01};

in U l a $32iiihoifiiiifi afit iliiei iliinhliiildi i fifiif; (methybapmhqmefi 1 Weight 9. 200 ft./min. are also possible. The permanent set of eias- 5 pagis 'i 'methygnefdlphenyl dnsocyfk tic filaments produced by the process of the invention gi gg g gzfi g33 2 31 5 2??? 332 3 1' n c ceptable ranges. A wind range of solvents may also be a -Spmnmg This 2 dope 18 then extrudgd used in the process of the invention. using the c0nd1t1ons described in Example 11. The prop- The elastic fibers and filaments of the invention are of these are ,also gwen Tab1e H shcwmfg useful in a variety of applications Such as in fabrics? the improvement in vertlcal short residence over horiwomens lingerie, support hose and similar textile end Zomal long resldence Splnmnguses- EXAMPLE IV The invention is further illustrated by the following examples in which all parts and percents are by weight un- A 4001mm Pomon by welght of a polyester Composed less otherwise indicated. In the examples the cited physical properties were measured on the Instron Tester, Model TM. Tenacity measurements are expressed in grams per denier (g.p.d.), the fibers being stretched at a rate of 1000 percent per minute. TElongation is the percent of polyethylene adipate and 20% polypropylene adipate, of molecular weight 1,690 was reacted with 124 parts of 4,4-methylenediphenyl diisocyanate in 286 parts dimethylformamide solvent for 2 hours. This prepolymer was added to a solution of 10 parts of m-xylylene diamine in 2740 parts of dimethylformamide to give a spinning dope. This spinning dope was extruded using the conditions described in Example II. The properties of the resulting fibers are given in Table II.

through the coagulating bath a distance of from 0.5 to 3.0 inches at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of from about 0.075 to 0.1 second.

TABLE II Example Spinneret Spin Bath Denier Elongation, Percent Stress Time (sec) Percent Retention EXAMPLE V 3. In the process for wet spinning of linear, segmented 100 itJmin. 170 fL/rnin.

Tenacity 1.07 0. 04 Elongation 588 560 Percent Sress Retained 80%, 2nd

Recovery 22. 1 21. 9

EXAMPLE VI The permanent set of fibers prepared from the polymer composition of Example I is improved when wet spun vertically as shown by the following data.

Percent set sample average): 2 secs. horizontal, 35;

0.075 sec. vertical, 28.

Similar improvement in elongation, tenacity, modulus, permanent set, stress retention and spinning speeds will be noted when other linear, segmented polyurethane compositions are wet spun according to the process of the invention.

The foregoing detailed description has been given for clearness of understanding only, and unnecessary limitations are not to be construed therefrom. The invention is not to be limited to the exact details shown and described since obvious modifications will occur to those skilled in the art, and any departure from the description herein that conforms to the present invention is intended to be included within the scope of the claims.

We claim:

1. In the process for wet spinning of linear, segmented polyurethane polymers to produce elastomeric polyurethane fibers and filaments, the improvement consisting of advancing the filaments as they are coagulated upwardly through the coagulating bath a distance of up to about 3.0 inches at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of up to about 0.2 second.

2. In the process for wet spinning of linear, segmented polyurethane polymers to produce elastomeric polyurethane fibers and filaments, the improvement consisting of advancing the filaments as they are coagulated upwardly polyurethane polymers to produce elastomeric polyurethane fibers and filaments, the improvement consisting of advancing the filaments as they are coagulated upwardly through the coagulating bath so that the filaments will move essentially vertically with respect to the surface of the coagulating bath liquid for a distance of from 1.5 to 2.0 inches at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of from about 0.075 to 0.1 second.

4. In the process for wet spinning of linear, segmented polyurethane polymers to produce elastomeric polyurethane fibers and filaments, the improvement consisting of advancing the filaments as they are coagulated upwardly through the coagulating bath consisting essentially of water and from 1 to 40 percent of dimethylformamide so that the filaments will move essentially vertically with respect to the surface of the coagulating bath liquid for a distance of from 1.5 to 2.0 inches at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of from about 0.075 to 0.1 second.

5. In the process for wet spinning of linear, segmented polyurethane polymers to produce elastomeric polyurethane fibers and filaments, the improvement consisting of advancing the filaments as they are coagulated upwardly through the coagulating bath consisting essentially of Water and from 1 to 40 percent of dimethylacetamide so that the filaments will move essentially vertically with respect to the surface of the coagulating bath liquid for a distance of from 1.5 to 2.0 inches at a rate of withdrawal which will result in the filaments remaining in the coagulating bath for a period of time of from about 0.075 to 0.1 second.

References Cited Hill, Rowland, editor, Fibres From Synthetic Polymers, 1953, Elsevier Publishing Company (Amsterdam- Houston-New York-London), pp. 379-388 and 461.

JAMES A. SEIDLECK, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

H. MINTZ, Assistant Examiner.

Patent No. 3 ,388 ,200 June 11 W68 Charles E. Jackson et al r appears in the above identified It is certified that erro e hereby corrected as patent and that said Letters Patent ar shown below:

Column 2, line 7, "2,9SS,07;" should read 2,955,017;

Lo Lumn 4 line 18 "varied grom 2 to O .75 seconds should read varied from 2 to 0 075 seeonds Signed and sealed this 10th day of March 1970 (SEAL) Attest:

\VILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patenk Attesting Officer 

